"Insurgents have made a combined attack on the base with the use of an explosive device installed on a truck by a suicide terrorist," defence minister Irakli Alasania said in televised comments.
"With great sorrow I must say that three Georgian servicemen were killed," he said, adding that there were an unspecified number of Georgian soldiers wounded.
Georgia has 1,570 troops serving in the Afghanistan's Helmand province, making the small Caucasus country of 4.5 million the largest non-NATO contributor to the International Security Assistance Force, according to the defence ministry.
All the attackers had been killed at the scene, Alasania said, and troops from Georgia's 42nd battalion had secured the area.
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At least 19 Georgian troops have been killed so far while serving in Afghanistan.
There are presently around 100,000 US-led NATO troops fighting a decade-long Taliban-led insurgency in Afghanistan.
Despite the stubborn insurgency, war-weary international forces are seeking to hand control of security to Afghan forces by withdrawing their combat troops by the end of 2014.
Georgia has said it is willing to continue deploying troops to assist local security forces after the NATO-led combat mission formally ends.